A sensor device is known in the art, according to which the sensor device has a combo sensor structure so that a gyro sensor (that is, an angular velocity sensor) and an acceleration sensor are formed in one package.
For example, according to a prior art disclosed in Japanese Patent No. 3,435,665, a combo sensor having two different kinds of dynamic quantity sensors is formed by use of a wafer level package (hereinafter, WLP). According to the prior art of this kind, the sensor has a structure in which a gyro sensor and an acceleration sensor are formed in a common sensor base plate, namely, the two sensors are formed in one chip. In the above prior art, the sensor base plate is sealed by a supporting plate and a cap layer.
More exactly, a capacitive type gyro sensor having a comb-teeth structure and a capacitive type acceleration sensor having a comb-teeth structure are arranged at positions neighboring to each other, in order to form those sensors in one chip. It is possible to reduce a size of the sensor device to some extent, when the combo sensor is formed by one chip.
However, in the sensor device of the above prior art as disclosed in Japanese Patent No. 3,436,665, there is no other ways than to reduce each of the sensors itself in size when it is necessary to further reduce the sensor device in its size as a whole, because the gyro sensor and the acceleration sensor are independently formed and arranged at the positions neighboring to each other. In addition, it is necessary to form a space between the sensors in order to avoid a situation that oscillation may be leaked from the gyro sensor to the acceleration sensor. As above, it is necessary in the above prior art to arrange the gyro sensor and the acceleration sensor at the positions neighboring to each other on a horizontal plane and to provide the space between those two sensors. Therefore, it is difficult to further reduce the size of the sensor device.
The sensor device having the gyro sensor and the acceleration sensor is explained above as the combo sensor. However, the same or similar problem exists in the sensor device having the gyro sensor and the dynamic quantity sensor of any other type than the acceleration sensor, when the gyro sensor and the dynamic quantity sensor are integrally formed.
For example, the same or the similar problem occurs in the sensor device, in which a surface acoustic wave (SAW) element is integrally formed with the gyro sensor. More exactly, it is necessary to form a space between the sensors in order to avoid a situation that oscillation may be leaked from the surface acoustic wave (SAW) element to the acceleration sensor.